The Bio-Rad galactomannan enzyme immunoassay (GM EIA) will soon be submitted to the FDA for approval as an aid to diagnose aspergillosis, a frequent cause of infectious death in immunosuppressed patients. Our preliminary studies suggest that the assay may also be used as a screening test to enable early diagnoses; however, the optimal cut-offs for positivity have not been determined. Defining cut-offs to optimize performance is critical for patients who have different manifestations of infection (endobronchial vs. invasive), such as in solid organ transplant recipients, and in children, who appear to have frequent false-positive results. The studies proposed in this project will define parameters to use the GM EIA in multiple different patient populations, using clinical samples obtained from a large ongoing FHCRC longitudinal protocol in adult allogeneic hematopoietic stem cell transplant (HSCT) recipients, and samples obtained from multicenter trials sponsored by the NIH. Aim 1 will define parameters for use of the GM EIA as an early diagnostic test for aspergillosis in adult allogeneic HSCT patients. Studies will be performed to determine the lower limit of GM detection, identify clinical factors that impact levels of circulating GM, and to determine the role of GM EIA applied to non-blood fluids (bronchoalveolar lavage fluid and urine). Aim 2 will define appropriate cut-offs for positivity and characterize performance of the GM EIA as a diagnostic assay for aspergillosis in high-risk solid organ transplant recipients. To do this, longitudinal sample collection will be performed in a protocol conducted as a companion to an ongoing CDC-sponsored multicenter surveillance study. Aim 3 will define parameters for use of the GM EIA as an early diagnostic test for aspergillosis in neutropenic children. To determine the appropriate cut-offs for positivity in children, GM EIAs will be performed on serial sera obtained from children at high risk for aspergillosis after treatment with induction chemotherapy for AML, and after cord blood transplant. Companion protocols will be performed to collect sera as part of ongoing multicenter studies performed by the Children' s Oncology Group and the NHLBI Cord Blood Transplantation Study. Studies will be performed to determine if false-positivity of the GM EIA in children corresponds with gut translocation of GM during periods of mucositis, by measuring surrogate markers for GI integrity in a case-control study. This project is enabled by the cooperative activities of FHCRC investigators, Bio-Rad Laboratories, and several multicenter networks supported by the CDC, NIAID, and NHLBI.